This disclosure relates generally to the field of image capture, and more particularly, to acquiring images with a wide “field of view” (FOV) image sensor.
“Field of view,” as used herein, refers to the angular extent of a given scene that is imaged by a camera. FOV is typically measured in terms of a number of degrees, and may be expressed as a vertical FOV, horizontal FOV, and/or diagonal FOV. The diagonal FOV of the image sensor is often referred to herein, as it is a more relevant measure of the camera's optics since it attempts to cover the corners of the image, where “roll off,” i.e., vignetting, problems associated with pixels at the corners of the image sensor may become more pronounced. For reference, a typical 35 mm camera with a lens having a focal length of 50 mm will have a horizontal FOV of 39.6°, a vertical FOV of 27.0°, and a diagonal FOV of 46.8°.
For a given camera-to-subject distance, lenses with focal lengths shorter than the sensor diagonal (commonly known as wide angle lenses) will distort perspective, such that objects that are closer to the camera appear to be larger than they would with a normal lens, and distant objects appear to be smaller and further away. Because of this distortion, wide angle lenses are not typically used for portraits. Likewise a normal lens (e.g., with a focal length approximately equal to the sensor diagonal) is not typically used for landscape photography because of the limited field of view.
The advent of portable integrated computing devices has caused a wide proliferation of cameras and video devices. These integrated computing devices commonly take the form of smartphones or tablets and typically include general purpose computers, cameras, sophisticated user interfaces including touch sensitive screens, and wireless communications abilities through Wi-Fi, LTE, HSDPA and other cell-based or wireless technologies. The wide proliferation of these integrated devices provides opportunities to use the devices' capabilities to perform tasks that would otherwise require dedicated hardware and software. For example, as noted above, integrated devices such as smartphones and tablets typically have one or two embedded cameras. These cameras generally amount to lens/camera hardware modules that may be controlled through the general purpose computer using firmware and/or software (e.g., “Apps”) and a user interface including the touch-screen fixed buttons and touchless control such as voice control.
The integration of cameras into communication devices such as smartphones and tablets has enabled people to share images and videos in ways never before possible. It is now very popular to acquire and immediately share photos with other people either by sending the photos via text message, SMS, or email, or by uploading the photos to an Internet-based service, such as a social networking site or a photo sharing site.
Along with the rise in popularity of portable integrated computing devices with integrated cameras has come a rise in the popularity of consumer photography. In particular, users often take so-called “selfies,” which are portrait or self-portrait photographs of the user of the device (and/or others in the user's proximity), typically taken with a front-facing camera on the device, i.e., a camera that faces in the same direction as the camera device's preview display screen. Most prior art cameras are optimized for either wide angle general photography or for self-portraits and video streaming use cases. Those cameras that are optimized for wide angles are optimized for group and landscape compositions, but are not optimal for portraits, due, e.g., to the distortion that occurs when subjects are at short distances from the camera. Those cameras that are optimized for portraits and video conference streaming (e.g., “front-facing” cameras) are not optimal for landscapes and group photos because of their limited field of view. Moreover, cameras on devices that face in the opposite direction of the device's preview display screen (e.g., “rear-facing” cameras) are typically designed with a short focal length and wide field of view, which is not optimal for portraits, due, e.g., to distortion caused at short distances from the camera. The field of view of a given camera also may influence how the user composes the shot and the quality of the ultimate captured image.